import path from 'path'
import tar from 'tar-stream'

import asyncHandler from '../utils/asyncHandler.js'
import bufferStream from '../utils/bufferStream.js'
import getContentType from '../utils/getContentType.js'
import getIntegrity from '../utils/getIntegrity.js'
import { getPackage } from '../utils/npm.js'
import serveBrowsePage from './serveBrowsePage.js'

async function findMatchingEntries (stream, filename) {
  // filename = /some/dir/name
  return new Promise((accept, reject) => {
    const entries = {}

    stream
      .pipe(tar.extract())
      .on('error', reject)
      .on('entry', async (header, stream, next) => {
        const entry = {
          // Most packages have header names that look like `package/index.js`
          // so we shorten that to just `/index.js` here. A few packages use a
          // prefix other than `package/`. e.g. the firebase package uses the
          // `firebase_npm/` prefix. So we just strip the first dir name.
          path: header.name.replace(/^[^/]+\/?/, '/'),
          type: header.type
        }

        // Dynamically create "directory" entries for all subdirectories
        // in this entry's path. Some tarballs omit directory entries for
        // some reason, so this is the "brute force" method.
        let dir = path.dirname(entry.path)
        while (dir !== '/') {
          if (!entries[dir] && path.dirname(dir) === filename) {
            entries[dir] = { path: dir, type: 'directory' }
          }
          dir = path.dirname(dir)
        }

        // Ignore non-files and files that aren't in this directory.
        if (entry.type !== 'file' || path.dirname(entry.path) !== filename) {
          stream.resume()
          stream.on('end', next)
          return
        }

        try {
          const content = await bufferStream(stream)

          entry.contentType = getContentType(entry.path)
          entry.integrity = getIntegrity(content)
          entry.size = content.length

          entries[entry.path] = entry

          next()
        } catch (error) {
          next(error)
        }
      })
      .on('finish', () => {
        accept(entries)
      })
  })
}

async function serveDirectoryBrowser (req, res) {
  const stream = await getPackage(req.packageName, req.packageVersion, req.log)

  const filename = req.filename.slice(0, -1) || '/'
  const entries = await findMatchingEntries(stream, filename)

  if (Object.keys(entries).length === 0) {
    return res.status(404).send(`Not found: ${req.packageSpec}${req.filename}`)
  }

  req.browseTarget = {
    path: filename,
    type: 'directory',
    details: entries
  }

  serveBrowsePage(req, res)
}

export default asyncHandler(serveDirectoryBrowser)
